Recent coverage said Classic McEliece became the first post-quantum algorithm to reach ISO standardization. That is not accurate. The same ISO amendment standardized two other post-quantum algorithms at the same time.
What the amendment contains
ISO/IEC 18033-2 Amendment 2 is the international standard for asymmetric ciphers, and its second amendment was published in June 2026. It added three key encapsulation mechanisms, the algorithms used to agree on a shared key over an open connection. The three are ML-KEM, FrodoKEM, and Classic McEliece.
ML-KEM is the one to notice. It is the same algorithm NIST published as FIPS 203, and it is the algorithm most vendors already ship. Its presence in the amendment means ISO did not create a competing track to NIST. ISO approved a set of algorithms, and the NIST choice is one of them.
The claim, corrected
The press release described Classic McEliece as the first post-quantum algorithm to reach ISO standardization. The accurate version is narrower. Classic McEliece is the first code-based algorithm ISO has standardized, which is a genuine milestone for code-based cryptography. It is not a first for post-quantum cryptography, because two other post-quantum algorithms are in the same document.
Where NIST and ISO differ
NIST ran a separate evaluation to choose a code-based algorithm. It compared Classic McEliece, BIKE, and HQC, and selected HQC in March 2025. NIST then left Classic McEliece to ISO rather than write its own standard for it, stating that concurrent standardization would risk incompatible standards and that McEliece is no longer under consideration in the NIST process.
So the two bodies now recommend different code-based algorithms. NIST points to HQC. ISO points to Classic McEliece. If your inventory only records “code-based algorithm,” that is no longer specific enough. It needs to record which algorithm, and which body approved it.
FrodoKEM and European rules
FrodoKEM is the third algorithm in the amendment. Germany's BSI recommends it for long-term confidentiality, and ENISA recommends it as well. European procurement documents will refer to FrodoKEM. An inventory built only around NIST will not have a place to record it, so the same system can look compliant under one set of rules and incomplete under another. The [PQ]time timeline tracks where each framework stands.
What a scan finds today
Standardization means an algorithm has an approved specification. It does not mean the algorithm is running anywhere.
Classic McEliece has very large public keys, between 255 KB and 1.3 MB. Keys that large do not fit the way TLS handshakes normally work, so servers do not offer the algorithm in ordinary web traffic. FrodoKEM has large keys for the same reason. A scan of live servers will almost never see either one.
ML-KEM is different. In its hybrid form, X25519MLKEM768, it is now negotiated on a growing share of connections, and the same measurements show how far behind origin servers run compared to the edge. The other two algorithms appear in the standard but rarely on the wire.
This is the same gap covered in our HAProxy guide. An algorithm being supported in theory is not the same as a server negotiating it in practice, and the only way to tell them apart is to measure the connection. Our origin posture dashboard shows that difference across real networks, where code-based key exchange is effectively absent from public web traffic.
What this means for your inventory
The ISO amendment changes what a cryptographic inventory needs to record. It adds one field: which standards track an algorithm follows, next to the field for the algorithm itself.
It does not change what a scan of your systems returns today. A scan still finds almost no code-based key exchange on the public internet. [PQ]probe records the algorithm each endpoint actually negotiates, on each port, against each framework's deadline, so the inventory reflects the live connection rather than the datasheet.
Sources:
- ISO/IEC 18033-2:2006/Amd 2:2026 — published June 2026, adds ML-KEM, FrodoKEM, and Classic McEliece
- Post-Quantum press release coverage — source of the “first PQC algorithm” claim
- NIST IR 8545, Status Report on the Fourth Round — HQC chosen over BIKE and McEliece, McEliece deferred to ISO
- NIST news: HQC announced as fourth-round selection — March 11, 2025
- FIPS 203, ML-KEM — the NIST-standardized lattice KEM
- Classic McEliece — parameter sets and key sizes
- FrodoKEM — ISO Amd 2:2026 standardization, BSI and ENISA recommendation
- Cloudflare Radar: origin post-quantum readiness — deployment share and origin-vs-edge measurement
Scan your endpoints with [PQ]probe to see which algorithms you actually negotiate.